EP0956271B1 - Device for intensive biological waste-water treatment - Google Patents

Abstract

The invention relates to a device for intensive biological waste-water treatment with freely moveable immersed biofilm, combined with mixing devices and, optionally, the introduction of air. The freely moveable immersed biofilm is used to immobilize specific micro-organisms in certain areas for waste-water treatment. In comparison with previously known devices, the invention is characterized in that the clarification process is more intensive due to the additional freely moveable, suspended/ floating immersed biofilm and its proportional oxygen supply from a special mixing device, provided upon emergence into the atmosphere in addition to aeration from fine bubbles. A substantially greater utilization of oxygen is obtained by enriching the air of the recycled sludge or waste-water through multiphase pumps. According to the invention, the activated sludge process is combined with the freely moveable immersed biofilm process in an installation. Said freely moveable biofilm is introduced into a sewage-treatment basin (1) as a biofilm carrier with an activated surface to immobilize specific micro-organisms in association with appropriate mixing devices (7) having a scooping effect due to paddles (3) and the proportion of activated sludge (6). Waste-water (4) flows through the sewage treatment basin (1) which comprises a retaining device (5) for the freely moveable immersed biofilm (2).

Description

The invention relates to a device for intensified biological wastewater treatment with freely moving immersion bodies in combination with mixing devices. Choice of fine-bubble aeration or liquid-gas mixture delivery with water-carrying internals. Freely moving immersion bodies with a settlement-friendly surface are used for the immobilization of specific microorganisms in the wastewater sector.

Various processes are used to purify waste water in sewage treatment plants. The activated sludge process without artificial or additional growth areas and a number of processes which use growth areas in the reactors are known. The use of so-called carrier biology is necessary. to intensify the clarification processes.
There are trickling filters. Immersion body method. Fixed bed reactors and the use of floating or floating biofilm carriers are known. These reactors are also referred to as biofilm reactors.

The advantages and disadvantages of the methods are described in DD 285 333 A5. A procedure is proposed in the cited document. which works with floating biofilm carriers. which protrude 1/3 to 2/3 above the water surface. A shaft in a horizontal position with disk-shaped bodies, in particular in the form of a screw conveyor, ensures the mixing and wetting of the growth immersion bodies.

Embodiments of immersion body processes are diverse and are described in EP 29 19 221.
EP 0 198451 and described in EP 0 385 011. This procedure is common. that they have a rotating immersion body. whose axis is arranged horizontally. A method is described in WO 92/01636. which in different. spatially separated stages works according to the immersion body method.

In the document WO 93/22244 and in JP-A 55 067 391, an immersion body method is described which contains the immersion bodies as freely movable growth carriers within defined zones of the rotating body.
The solution in WO 86/05770 and DE 195 14 931 A1 also works with growth carriers enclosed in a rotating body. In the latter method, the growth carriers are moved by blades arranged immovably on the inner circumference of a cylinder drum.
A similar process is proposed in EP 32 38 366, here the growth supports are arranged in chambers in a fixed bed-like manner and the rotating fixed bed is alternately surrounded by air and waste water due to the variable level of the waste water. Furthermore, the separation into different zones is described and also specified in terms of equipment.

The compacting of the growth areas of immersion body systems in the critical zones causes malfunctions in the mixing and separation and leads to a reduction in cleaning performance and is to be mentioned as a disadvantage of carrier fixation. With thick biofilms, diffusion is limited and the risk of clogging of the wearer is high. The mining processes are then difficult to control.
For this reason, conventional activated sludge processes are most often implemented despite the high space requirement.

Other important criteria for the effectiveness of clarification processes are the mixing and the amount of air in the process. Various solutions are also described for this. DE 42 38 912 A1 proposes the construction of a rotation system by means of which turbulence and air entry are made possible in a simple manner.

The various degradation reactions have already been addressed with their different degradation conditions and the associated reaction zones. The zonal separation of phosphorus and nitrogen elimination is described for example in DE 4409 435.
There are approaches to combine the advantages of different processes, for example the immersion process and the activated sludge process. Such a process is known as the Stählermatic process. The combination of advantages is necessary in order to meet increasing requirements for discharge values of wastewater and to take into account the fact that spatial extensions of the sewage treatment plants are usually not possible due to costs and space constraints.

Proceeding from this prior art, the object of the invention is to intensify the clarification process. Furthermore, a maximum proportion of well distributed and clog-free vegetation areas in the aeration basin should be realized with energetically optimized ventilation.

The concept according to the invention is based on an optional combination of device elements for the activated sludge process with fine-bubble aeration or liquid-gas mixture delivery, as well as for the process with freely moving immersion bodies and a special mixing device.

In the entire wastewater treatment basin, freely moving immersion bodies are introduced as biofilm carriers with an activated surface for the immobilization of specific microorganisms in combination with suspended activated sludge flakes and increase the concentration of biologically active microorganisms compared to a basin with only suspended activated sludge. The wastewater flows through the wastewater treatment basin and contains a retaining device for the freely moving immersion bodies.

Due to mechanical influences on the one hand and biological growth on the other hand, a biofilm thickness is achieved on the growth support, which enables a favorable ratio of surface and ventilation intensity, whereby growth and detachment or abrasion is brought into equilibrium, which achieves optimal mass transport in relatively thin biofilms and a relatively even distribution of the immobilized microorganisms on the vegetation areas.

The movement of the mixing device limits the growth in thickness of the biofilm on the freely movable immersion bodies with the help of the mechanical stress on the immersion bodies moved relative to one another as a result of turbulence and abrasion and thus ensures the optimization of mass transport, oxygen supply and degradation performance.

The structure of the plant according to the invention increases the effective growth areas with improved colonization conditions for special microorganisms. This is achieved through the use of special materials for the growth immersion bodies, such as xylith and HDPE-REC.
Modified polypropylene is also used as the material for the freely movable immersion bodies and for the growth surfaces integrated in the device. The geometry of the paddles of the mixing device is designed so that the paddles can move large amounts of growth immersion bodies and lift them out of the water, growth areas for microorganisms can be provided in the paddles and the oxygen supply to the microorganisms is additionally improved by air enrichment of return sludge. The mixing device consists of radiation-shaped carriers which are provided with paddles which are arranged at different distances from the center of the mixing device.

Furthermore, in order to increase the oxygen utilization when air is introduced into the return sludge in the lower part of the waste water treatment basin, the mixture of return sludge and waste water enriched with air can be forced into channels. The walls of these channels have a surface that is friendly to microorganisms.

Due to the special mixing device, consisting of beams arranged in a beam shape with paddles provided on these supports, there is a relative uniform distribution of the floating immersion bodies in the desired zones of the treatment basin, as well as the aeration of the biofilms in portions by lifting part of the immersion bodies out of the water the atmosphere instead.

The higher biomass concentration enables the reaction rooms and the clarification volume to be reduced. A high degree of process stability with respect to fluctuating feed conditions is achieved by evenly distributing the biomass on the carrier material. The nitrification and simultaneous denitrification in the biofilm is supported by anoxic sub-zones and intermittent aeration. The enrichment of the biofilm with slowly growing organisms leads to the further elimination of poorly degradable organic substances. The swelling and swimming sludge formation is thus kept low.

The amount of biologically produced sewage sludge is reduced compared to the biological excess sludge of an activated sludge system with only suspended flakes of the microorganisms and conventional immersion processes. With sludge stabilization, it meets the requirements for agricultural sewage sludge recycling.

Another advantage of the device according to the invention is the unproblematic extensive expansion of existing plants by designing arbitrarily large wastewater treatment basins in the horizontal direction (one behind the other, next to one another) in contrast to devices which are bound to vertical wastewater flows and are therefore technically and economically restricted by the height.

The sludge age is increased due to carrier fixation and nitrificants can grow better, whereupon the cleaning performance increases and the residence times of the waste water are shortened.
As a result of the increase in the oxygen-consuming area, it is possible to work in the transition area from oxic to anoxic mode of operation analogously to the method of simultaneous aerobic sludge stabilization. In the anoxic sub-zones, denitrification, simultaneous sludge stabilization and biological phosphorus elimination of the activation volume are expanded and specifically promoted. Another advantage of the invention is the simple expansion of the capacity of existing systems by integrating the newly developed components and the effective elimination of the nitrogen and phosphorus compounds.

Fig. 1:

Abwasserbehandlungsbecken mit Paddeln

Fig. 2:

Abwasserbehandlungsbecken mit zwei Zonen, verschiedenen Aufwuchstauchkörpern und Paddeln und zusätzlicher Belüftungseinrichtung

Fig 3:

Schematische Darstellung eines Abwasserbehandlungsbeckens mit 3 Zonen

Fig. 4:

Schnittprofile von Paddeln

Fig. 5:

Vorrichtung mit Luftanreicherung des Rücklaufschlammes

Fig. 6:

Schnittprofil eines doppelwandigen Paddels mit Zwischenraum und Xylithfüllung

Fig. 7:

Schnittprofile von Paddeln mit Aufnahmeblechen

Fig. 8:

Ausgestaltung der Paddel als Körbe

To further explain the invention, reference is made to the claims. Details, features and advantages of the invention result from the following description of exemplary embodiments with reference to the associated drawings. Show it:

Fig. 1:

Wastewater treatment pool with paddles

Fig. 2:

Wastewater treatment pool with two zones, different growth plungers and paddles and additional aeration device

Fig 3:

Schematic representation of a wastewater treatment basin with 3 zones

Fig. 4:

Cutting profiles of paddles

Fig. 5:

Device with air enrichment of the return sludge

Fig. 6:

Sectional profile of a double-walled paddle with space and xylith filling

Fig. 7:

Cut profiles of paddles with mounting plates

Fig. 8:

Design of the paddles as baskets

A single-basin system for intensified biological wastewater treatment with the help of freely moving immersion bodies 2, mechanical mixing 3, 7 and zonal activated sludge fraction 6 in a reaction chamber filled with waste water 4 is shown in FIG. 1. The mixing device 7 can be designed with paddles 3.

The single-basin system combines the high and low load levels of wastewater treatment and is carried out with or without (in the system shown) additional ventilation via the floor. The growth immersion bodies 2 consist of a plastic agglomerate with a strongly structured surface and a grain size of 10-15 mm, or of xylith, a natural substance in the form of fossil plant remains. which are a by-product of lignite mining and are available at low cost and immobilize nitrifying agents in particular. The reference numerals 1 and 5 also entered in FIG. 1 stand for the waste water treatment basin 1 and for the retention device 5.

A system in the combination of mixing device 7 with paddles 3 and freely movable growth immersion bodies 2 and activated sludge fraction 6 is shown in FIG. 2. Specific microorganisms are immobilized in separate reaction rooms, each of which has a mixing device 7 with paddles 3. The waste water treatment basin 1 is divided by a partition 10 into two zones 8 and 9, which are connected to one another through openings at the bottom of the waste water treatment basin. A sieve-shaped installation acts as a floor retention device 12 for growth immersion bodies 2 and is kept free of blockages by a specially directed air inlet nozzle 13. The zones are mixed by mixing devices 7, which can be designed both as paddles 3 and as other rotating immersion bodies. Brushes or scrapers 14 are installed on the geometrical outer circumference of the mixing devices in order to keep the retaining device 5 free from growth immersion bodies 2. The restraint device 5 is designed as a baffle in this exemplary embodiment. Aeration devices 11 are provided on the bottom of the wastewater treatment basin 1 for additional ventilation or the introduction of atmospheric oxygen. The entry of atmospheric oxygen is regulated zone-specifically via compressors.

The creation of optimal specific living conditions for the microorganisms in the reaction zones for the removal of dirt and nutrients is achieved by the variation of the carrier material, its share in the total volume and the oxygen input through the compressor and / or mechanical circulation. The oxygen supply to the growth surfaces of the growth immersion bodies 2 is achieved by lifting them out or the scooping effect of the paddles (scooping profiles) 3. The lifting of the growth immersion bodies 2 and the subsequent immersion at another point in the respective zone 8, 9 ensures an intensified ventilation effect. A better utilization of oxygen is also made possible by the bulging immersion bodies 2, which agglomerate and act in a loose, two-dimensional composite, by retaining and hindering the bubbling of the air bubbles entered on the ground via the ventilation devices 11, 13.

In the first zone 8 bodies made of HDPE-Rec, a plastic recycling material with a structured surface, and in the second zone 9 bodies made of xylith are used as growth immersion bodies 2. Instead of xylith, the nutrient-enriched plastic agglomerates described in more detail below are also used advantageously in this zone. The choice of material for the growth immersion bodies 2 supports nitrification, denitrification and sludge stabilization in the zones.

Furthermore, special freely movable immersion bodies 2 are used, which are formed by agglomeration, for example by fusion by means of frictional heat. These special freely moving immersion bodies 2 can be constructed from different basic materials. The basic materials consist chemically of the plastic polypropylene. The combination of different base materials is advantageous, which leads to targeted surface properties and structures. The surface of the agglomerates is greatly enlarged and colonization-friendly for microorganisms.

As basic materials, the components PPH 2150 and PPH 2250 are agglomerated into growth immersion bodies 2 by the company Hoechst, for example. Products from BASF with Novoden 1300 Z and PCD with Daplen BE 50 represent further basic materials. Various combinations of the basic materials are possible.

The addition of nutrients to the base materials before agglomeration is particularly advantageous. The added nutrients offer the microorganisms optimal living conditions in finest to coarse distribution in the growth immersion bodies 2 and promote the settlement and growth of the microorganisms.

An additional effect is surprisingly achieved by adding nutrients to the growth immersion bodies 2. It is possible to settle specific microorganisms on the growth immersion bodies 2 by the targeted addition of carbon, nitrogen or phosphorus compounds. Enriched immersion bodies 2 enriched in this way are used differently in the wastewater treatment zones.

Fig. 3 shows a schematic representation of a 3-stage wastewater treatment plant. Two zones 8, 9 with mixing devices 7 operating over the entire height are followed by a zone 15 with two opposing mixing devices 7, which intensely enter atmospheric oxygen at the liquid surface.

Alternatively or in addition to the fine-bubble aeration, the oxygen supply for the sessile and suspended microorganisms in the biological process stage is achieved by the air enrichment of the return sludge conveyed from the secondary clarification into the waste water treatment basin 1. Through the active and intensive mixing of the liquid and gas phases with conveying and mixing elements, eg multi-phase pumps, a high degree of dispersion is achieved and the atmospheric oxygen is directly deposited on the recycled biomass. The degree of dissolving of the air entered can reach up to 100%. When entering the wastewater treatment basin 1, 21 bubbles with a diameter of approx. 30 µm with a large surface for gas exchange are formed depending on the saturation pressure during the relaxation of the return sludge-air mixture, which in turn leads to a high utilization of oxygen by the microorganisms in the wastewater treatment basin 1 leads.

In order to increase the oxygen utilization when air is introduced into the return sludge via active conveying and mixing elements or when air is introduced via a compressor into the return sludge or into the wastewater 4, the return sludge-air mixture 21 mixed with the wastewater 4 is forced into a channel system in the lower part of the basin. 5 shows how the dwell time of the air in the wastewater stream is lengthened by horizontally arranged channels 19 and thus the oxygen utilization by the microorganisms is significantly improved. The channel walls 20 can be formed as plastic plates with surfaces that are friendly to microorganisms and structured, which leads to a further increase in the sessile portion of the microorganisms in the device. The flow cross-sections of the channels 19 are designed so that there is a sufficient flow velocity that prevents the sludge flakes of the return sludge from settling in the channels 19.
In the upper area of the wastewater treatment basin 1, the entry of atmospheric oxygen is secured via the freely movable immersion bodies 2.
An anoxic zone 22 can be created below the freely movable immersion immersion bodies 2 and above the channel internals via a controlled system with measurement of the O ₂ content in the wastewater treatment basin 1 and control of the air entry.
A further advantageous embodiment is the combination of the freely movable immersion body 2 with a fixed bed, the channels of which are flowed through obliquely and vertically from bottom to top, the air being introduced at the bottom of the pool.

The design of the paddles 3 is of great importance for the efficiency of the system. In addition to the basic shapes shown in FIG. 4, the paddles 3 can advantageously be designed in a double-walled design. 6 is shown. how the space 16 of a double-walled paddle 3 is filled with fibrous xylith 17. This provides additional, intensely ventilated growth areas for the microorganisms through which wastewater flows. By lifting the paddles 3 into the atmosphere there is an adequate supply of oxygen to the microorganisms on the xylith 17. Excess oxygen is released into the water by diffusion when immersed.

A further advantageous enlargement of the growth area and the amount of moving growth immersion bodies 2 are represented by the receiving plates 3.1 sketched in FIG. 7. The various basic shapes of the paddles 3 can be provided with the receiving plates 3.1 in order to increase the receiving capacity.

FIG. 8 shows how the paddles 3 are designed as baskets 18 to further increase the effectiveness of the device. The baskets 18 are used to lift and aerate a larger number of immersion bodies 2 from the water.

LIST OF REFERENCES

1

Wastewater treatment basin

2nd

freely moving immersion bodies

3rd

Paddle (scoop profiles)

3.1

Mounting plates

4th

sewage

5

Restraint device for freely moving immersion bodies

6

Activated sludge content

7

Mixing devices

8th

Zone 1

9

Zone 2

10th

partition wall

11

Ventilation equipment

12th

Floor restraint

13

Air inlet nozzle

14

Brush / scraper

15

Zone 3

16

Space

17th

Xylith

18th

baskets

19th

channel

20th

Canal wall

21

Return sludge-air mixture

22

anoxic zone

Claims (21)

1. Device for intensive biological waste-water treatment that consists of a waste-water treatment basin (1) and immersed biofilm bodies (2) free to move whereby a number of these freely moving immersed biofilm bodies (2) are lifted from the waste-water treatment basin

   (1) by a mixing device (7) thereby scooping, during mixing are temporarily inside, temporarily outside of the waste water (4) and simultaneously are rolled in the basin by the mixing device (7),
   characterized in that the mixing device (7) consists of radial carriers which are equipped with paddles (3) whereby the paddles (3) are movably arranged in different distances from the centre of the mixing device (7) and, further, the freely moving immersed biofilm bodies

   (2) are distributed over and free to move in the entire waste-water treatment basin (1) and are held in the waste-water treatment basin (1) by detention devices (5).
2. Device to Claim 1
   characterized in that the freely moving immersed biofilm bodies (2) consist of xylite and preferably immobilize nitrifying bacteria.
3. Device to Claim 1
   characterized in that the freely moving immersed biofilm bodies (2) consist of a plastic recycling material with structured surface, high-pressure polyethylene LDPE-REC.
4. Device to Claim 1
   characterized in that the freely moving immersed biofilm bodies (2) and/or biofilm surfaces integrated into the device consist of polypropylene.
5. Device to Claim 4
   characterized in that the freely moving immersed biofilm bodies (2) as agglomerates are made from various basic materials and have an intensely structured surface.
6. Device to Claim 5
   characterized in that the basic materials of the freely moving immersed biofilm bodies (2) have been agglomerated by thermal effects.
7. Device to Claim 5 or 6
   characterized in that the freely moving immersed biofilm bodies (2) have a grain size of 6 to 20 mm.
8. Device to any of the Claims 4 to 7
   characterized in that the freely moving immersed biofilm bodies (2) and/or the biofilm surfaces of polypropylene integrated into the device contain nutrients for microorganisms.
9. Device to any of the Claims 2 to 8
   characterized in that the immersed biofilm bodies (2) are arranged in swimming and/or suspended condition due to a small difference in their density to that of the waste water (4) in the required zones of the treatment basin with a relative equidistribution.
10. Device to Claim 1
    characterized in that the waste-water treatment basin (1) is divided by a partition (10) into, at least, two zones (8, 9) which are connected with each other near to the bottom of the waste-water treatment basin (1) or near to the surface by openings, and there are mixing devices (7) with paddles (3) in the zones (8, 9).
11. Device to Claim 10
    characterized in that the immersed biofilm bodies (2) consist of LDPE-REC in the first zone (8) and of xylite or plastic agglomerates enriched with nutrients in the second zone (9).
12. Device to Claim 1
    characterized in that the paddles (3) consist of perforated surfaces or flat formed bodies permeable to water.
13. Device to Claim 12
    characterized in that the surfaces permeable to water are made as punched plates.
14. Device to any of the Claims 1 to 13
    characterized in that the paddles (3) are double-walled and xylite (17) or immersed biofilm bodies (2) are placed in the spaces (16) between the walls.
15. Device to any of the Claims 1 to 14
    characterized in that the paddles (3) are designed as baskets (18).
16. Device to any of the Claims 1 to 15
    characterized in that the paddles (3) and/or the baskets (18) contain additional gathering plates (3.1).
17. Device to Claim 1
    characterized in that for fine-sparkling aeration, aeration devices (11) are provided at the bottom of the waste-water treatment basin (1) able to control the air oxygen infeed specific to the zone.
18. Device to Claim 1
    characterized in that the oxygen infeed into the waste-water treatment basin (1) is realized by the infeed of air into the return sludge or the waste water (4) using multiple-phase pumps for liquid-gas mixture delivery or takes place additionally to the fine-sparkling aeration.
19. Device to Claim 18
    characterized in that in the lower part of the waste-water treatment basin (1) the mixture of return sludge (21) and waste water (4) enriched with air oxygen is forced to flow in channels (19).
20. Device to Claim 19
    characterized in that the channels (19) are confined by channel walls (20) that have a structured surface positive towards the settling of microorganisms.
21. Device to Claim 20
    characterized in that the channels (19) are arranged horizontal or with a slight slope and are passed from below upwards.